Phenol from haloaromatics



United States Patent 3,213,146 PHENOL FROM HALOAROMATICS Walter H.Prahl, Buffalo, and Sol J. Lederman, Kenmore,

N.Y., assignors to Hooker Chemical Corporation, Niagara Falls, N.Y., acorporation of New York No Drawing. Filed Aug. 25, 1961, Ser. No.133,802 Claims. (Cl. 260-629) This invention pertains to the productionof phenol and more specifically to the production of phenol by thevapor-phase catalytic hydrolysis of polychlorobenzene, or chlorophenol.

It is known that phenol can be produced by the hydrolysis ofmonochlorobenzene in vapor phase over catalysts, according to theoverall reaction:

The hydrolysis catalysts used in this reaction are oxides, hydroxides orsalts of the elements of columns 1 to 4 of the periodic system. Examplesof catalysts especially suitable are silicon dioxide, aluminum oxide andtricalcium phosphate. The catalytic activity of these catalysts can beincreased by the use of compounds of copper, nickel and similar heavymetals as promoters, as described, for instance, in US. Patent1,964,768.

If, instead of monochlorobenzene, the same reaction were applied todichlorobenzenes, the formation of dihydroxybenzenes would be expected,which however, under prevailing conditions, would be expected todecompose, so that the vapor-phase hydrolysis of dichlorobenzenes wouldnot be expected to lead to useful products.

Further, certain (11-, tri-, and tetrachlorobenzenes have been in excesson the market at times. These polychlorobenzenes come from many sources.For instance, in the catalytic oxychlorination of benzene with HCl andair to form monochlorobenzene, certain quantities of dichlorobenzenesare produced as a by-product. Lesser amounts of tri-andtetrachlorobenzenes are also produced. Furthenin the direct chlorinationof benzene, polychlorobenzenes are produced as by-products for whichthere has been an insufficient market.

However, there has been an increasing market for phenol especially foruse in the plastics field which has required further construction orexpansion of plants for meeting this enlarging demand, as well asseeking other routes to the production of phenol.

Therefore, it is an object of this invention to provide a new method forthe production of phenol.

Another object is to provide new starting materials for the productionof phenol.

Still another object is to provide a method for converting thepolychlorobenzenes and chloro phenols which are formed as undesirableby-products in several industrial processes into salable or usefulproducts.

A further object is to provide a method of recovering the organic andchlorine content of polychlorobenzenes in a commercially useful form.

Other objects become apparent in the course of this description.

According to the present invention, we have unexpectedly found that ifpolychlorobenzenes or chlorophenols in vapor phase, together with watervapor, are passed over the catalysts conventionally used for theproduction of phenol from monochlorobenzene, phenol is formed. Althoughwe do not wish to be limited to any theories except as defined in theappended claims, the overall reaction appears to be illustrated asfollows:

C H Cl -l-H O +H C H OH+2HCl In other words, one of the chlorine atomsof the dichlorobenzene molecule appears to undergo hydrolysis in theexpected form, but the other appears to be replaced 3,213,146 PatentedOct. 19, 1965 by hydrogen in a hydrogenolysis, rather than by theexpected hydroxyl group. The hydrogen is apparently formed in situ. Thistheory tends to be confirmed by our further discovery that ifmonochlorophenols are subjected to the same reaction conditions, themain reaction leads toward the formation of phenol by replacement of thechlorine with hydrogen, rather than with a hydroxyl radical.

We have found further that the conversion of polychlorobenzenes orchlorophenol to phenol can be carried out under essentially the sameconditions under which the conventional and customary hydrolysis ofmonochlorobenzene is effected; that is, at temperatures between about250 degrees Centigrade up to about 600 degrees centigrade, withtemperatures between about 400 degrees centigrade and 500 degreesCentigrade being preferred.

The ratio of polychlorobenzene to water can vary within wide limits.When dichlorobenzene is used, the range of about one third to about fourmoles of dichlorobenzenes to one mole of water is preferred.

We have found that the yield, that is the percentage of phenol formed inrelation to the quantity of starting material consumed in the reaction,decreases with increasing conversion. The term conversion herein isdefined as the percentage of starting material fed into the reactionwhich reacts. The choice between a high yield of phenol at lowconversion with larger equipment and larger consumption of utilities fora given production, or a lower yield of phenol at a higher conversion,with smaller equipment and less consumption of utilities for a givenquantity of phenol, is a matter of economics. Our preferred range isbetween approximately eight percent and twenty-five percent conversion,but conversions outside of this range are technically and sometimeseconomically feasible.

The substances which can be used as starting materials in this inventionare compounds having the structure:

where Y is either a chloro-radical or a hydroxyl group, Cl is achloro-radical and n is an integer from zero to two. These compounds areortho, meta-, and paradichlorobenzene, ortho-, meta-, andpara-monochlorophenol, 1,2,3-, 1,2,4-, and 1,3,5-trichlorobenzene,1,2,'3,4-, l,2,4,5-, and 1,2,3,S-tetrachlorobenzene, diandtrichlorophenol.

We have further found that the reaction according to this invention canbe carried out simultaneously with the conventional hydrolysis ofmonochlorobenzene to phenol. For that purpose mixtures ofmonochlorobenzene, polychlorobenzene and/or chlorophenols can be passed,together with water in vapor form over catalysts to form phenol, ratherthan being separated from the monochlorobenzene and sold as by-products,as was done in the past.

The following examples are given to further illustrate our invention,but we do not wish to be limited to these except as defined in theappended claims. In ,each of the examples below the catalyst wascontained in a two and one-half inch diameter steel pipe and kept at thereaction temperature by immersion in a fused salt bath.

Example 1 Six hundred and seventy-three grams of a five percent byweight mixture of ortho-chlorophenol in chlorobenzene and 394 grams ofwater were passed, as vapor, over 500 cubic centimeters of a tricalciumphosphate catalyst at about 420 degrees centigrade during a six hourperiod of time. The amounts of exit materials recovered showed that0.178 mole of chlorobenzene and 0.197 mole of chlorophenol had reacted.Hydrochloric acid (0.3075 mole), and phenol (0.261 mole) were producedtogether with 0.042 mole of benzene.

Of the 1067 grams of liquid feed, 1062 grams of liquid products wererecovered; in addition, 4050 cubic centimeters of gases were collected.

The comparison of the hydrogen chloride and phenol yields shows that0.85 mole of phenol are formed per mole of hydrogen chloride, and 0.137mole of benzene.

Example 2 Dichlorobenzene (946 grams), was passed, with water (305grams) as vapor, over a catalyst consisting of silica gel impregnatedwith cupric chloride at 385 degrees centigrade over a period of fourhours. All but 43 grams of the dichlorobenzene was recovered unreacted.Of the dichlorobenzene converted, 36 percent yielded orthochlorophenol,8 percent phenol and 10 percent chlorobenzene.

Example 3 Ortho-chlorophenol (188 grams), and water (130 grams), werepassed over a tricalcium phosphate catalyst at about 420 degreescentigrade. All but 0.237 mole of chlorophenol were recovered unreacted.There were produced 0.23 mole of hydrogen chloride, together with 0.183mole of phenol, and 0.0275 mole of chlorobenzene. There were collected4150 cubic centimeters of gas, and this together with the carbondeposited on the catalyst accounted for 0.0151 mole of chlorophenol.Therefore, of the unrecovered chlorophenol, the following percentageswere converted to these products: phenol, 77.2 percent, chlorobenzene,11.6 percent, and C, C0, C 6.4 percent.

Example 4 A solution containing 7.3 percent (by weight), of diandhigher-chlorobenzenes in monochlorobenzene was passed at the rate of 150cubic centimeters an hour, with 60 cubic centimeters an hour of waterover 500 cubic centimeters of tricalcium phosphate catalyst at 400 degrees centigrade. Of the dichlorobenzenes which reacted, 69.5 percentwas converted to phenol, 12.3 percent to chlorophenols, 14 percent tobenzene, and 4 percent to waste products.

Example 5 1,2,4,5-tetrachlorobenzene, (4254 grams), was passed, togetherwith water (3710 grams), over a tri-calcium phosphate catalyst at about400 degrees Centigrade during a period of fifteen hours. The phenolicproduct consisted of 1.4 percent phenol, 3.6 percent2,4,5-trichlorophenol, and 16 percent of 2,5-dichlorophenol. Thenon-phenolic material consisted of the original starting material (95percent), and 1,2,4-trichlorobenzene (4.6 percent).

Example 6 During a period of six hours, 1542 grams of a mixtureconsisting of 8.6 percent dichlorobenzenes, 77.5 percenttrichlorobenzenes, and 13.9 percent tetrachlorobenzenes were passed,with 360 grams of water, over a tricalcium phosphate catalyst at about400 degrees centigrade. The products contained 3.85 grams of phenol,29.68 grams of chlorophenol, 2.81 grams of dichlorophenol, and 0.67 gramof tar.

From a consideration of the above examples, especially Examples 1 and 4,it is clear that this invention can be particularly useful in theso-called Raschig-phenol process for the reaction of benzene in a firstchlorination stage using hydrogen chloride and .air to producechlorobenzene followed by a second hydrolysis stage to hydrolyze thechlorobenzene to phenol. With this invention, the polychlorobenzenesformed as by-products in the first stage and the chloro phenols formedas by-pr-oducts in the second stage, which by-products were up until nownot usable in the process, can be used as feed to the second stage andconverted to phenol, and thereby increase the overall yield of phenoland reduce the amount of byproducts.

Various modifications can be made to our examples and disclosure,without departing from the scope of our invention, and we do not wish tobe limited hereto except as defined in the appended claims.

We claim:

-1. In the continuous process for the production of phenol by theoxychlorination of benzene to monochlorobenzene and polychlorobenzene in.a first chlorination stage, followed by the hydrolysis in a secondstage of rnonochlorob'enzene with steam to phenol (and H01 in vaporphase over a tricalcium catalyst therefore at a temperature betweenabout 250 and about 600 degrees centigrade, the improvement whichcomprises introducing as lfeecl to the said second stage saidpiolychlorobenzenes along with the rn-onoch lorobenzene, whereby phenol(C H OI-l) is produced from the said polychliorobenzenes as well .asfrom the monochlorobenzene.

2. The process according to claim 1 wherein the feed to the said secondstage consists essentially of steam, monochlorobenzene landdichlorobenzene.

3. In the continuous process for the production of phenol by theoxychlorination of benzene to monchloro-- benzene and polychlorobenzenesin a first chlorination stage, followed by the hydrolysis in a secondstage of monochlorobenzene with steam to phenol and HCl in vapor phaseover a tricalcium phosphate catalyst therefor at a temperature betweenabout 250 and about 600 degrees centi-grade, the improvement whichcomprises introducing as feed to the said second stage saidpolychlorobenzenes and a chlorophenol containing from one to threechlorine atoms :along with the monochlorob enzene, where- 'by phenol (CI-I 0H) is produced from the said polychloro'benzenes and chlorophenolas well as from the monochlorobenzene.

4. The process according to claim 3 wherein the feed to the said secondstage consists essentially of steam, monochlorobenzene, dichlorobenzeneand chlorophenol.

5. The process according to claim 3 wherein the feed to the said secondstage consists essentially of steam, rnonoch'lorobenzenedichlorobenzene, trich-lorobenzene and a chl-orophenol containing fromone to three chlorine 'atoms.

:6. The process for the production of phenol which comprises passing inthe vapor phase materials consisting essentially of water,monoohlorobenzene and polychlo-robenzene at a temperature between about250 and about 600 degrees centi-grade in the presence of a tricalciumphosphate catalyst, the mole ratio being from about onethi-r-d to aboutfour moles of said monochlorbenzene and polychloro benzene per mole ofWater, whereby phenol (CgH OI-I) is produced from saidpolychlor-obenzene as Well .as from said monochloro'benzene.

7. The process for the production of phenol which comprises passing inthe vapor phase materials consisting essentially of water,monochlorob-en-zene, a chlorophenol containing from one to threechlorine atoms, and polychlorobenzene at a temperature between about 250and 600 degrees centignade in the presence of a tricalcium phosphatecatalyst, the mole ratio being about one-third to where Y is selectedfrom the group consisting of a dhflororadical and a hydroxyl group, andn. is an integer firorn zero to two, at a temperature between about 2/50and 600 degrees centi g-rade in the presence of la tricalcium phosphatecatalyst, the mole ratio of said material being from about one-third toabout iour moles per mole of water, whereby phenol (C H OH) is soproduced.

6 9. A process according to claim 8 wherein the said materialpolychlonobenzene.

10. A process according to claim 8 wherein the said material is aohlorophenol containing from one to three clhlorine atoms.

References Cited by the Examiner UNITED STATES PATENTS 1,849,844 3/82Lloyd et a1 260- 623 X 1,966,281 7/34 Bertsch 260-629 2,766,295 10/56Gleim Q=62J1 2,803,669 8/57 Brainerd et a1 2 60-6 21 FOREIGN PATENTS575,229 5/59 Canada.

LEON ZITVER, Primary Examiner.

CHARLES B. PARKER, Examiner.

1. IN THE CONTINUOUS PROCESS FOR THE PRODUCTION OF PHENOL BY THEOXYCHLORINATION OF BENZENE TO MONOCHLOROBENZENE AND POLYCHLOROBENZENE INA FIRST CHLORINATION STAGE, FOLLOWED BY THE HYDROLYSIS IN A SECOND STAGEOF MONOCHLOROBENZENE WITH STEAM TO PHENOL AND HCL IN VAPOR PHASE OVER ATRICALCIUM CATALYST THEREFORE AT A TEMPERATURE BETWEEN ABOUT 250 ANDABOUT 600 DEGREES CENTIGRADE, THE IMPROVEMENT WHICH COMPRISESINTRODUCING AS FEED TO THE SAID SECOND STAGE SAID POLYCHLOROBENZENESALONG WITH THE MONOCHLOROBENZENE, WHEREBY PHENOL (C6H5OH) IS PRODUCEDFROM THE SAID POLYCHLOROBENZENES AS WELL AS FROM THE MONOCHLOROBENZENE.